Video memory is something that needs to be adjusted in the BIOS of the computer. Sometimes computer manufacturers set a specific amount of video memory the system will be able to use and then they lock the setting. You can try accessing the BIOS of your ASUS* laptop and look for graphics memory option. If you do not find any setting related to video memory then most likely it was locked.

You can also try contacting ASUS* in order to check with them what is the maximum amount of video memory they have configured in that specific laptop model. This link will give you their contact information https://www.asus.com/us/support/